Safety device for gas fired boilers



Dec. 28, 1965 G. H. FAMILQ 3,225,816

SAFETY DEVICE FOR GAS FIRED BOILERS Filed Aug. 10, 1962 INVENTOR.

GEORGE H. FAMILO BY (MA m Km United States Patent 3,225,816 SAFETY DEVICE FOR GAS FlRED BOILERS George H. Familo, Oswego, N .Y., assignor of fifty percent to Harvey J. Tucker, Syracuse, N.Y. Filed Aug. 10, 1962, Ser. No. 216,198 11 Claims. (Cl. 158-125) This invention relates to a safety device for gas-fired boilers. More particularly, it relates to a device for preventing explosions in a boiler combustion chamber in which the burner is alternately ignited and turned oil automatically in response to thermosensitive controls.

One well-known type of gas fired boiler employs a remotely controlled shut-01f valve for turning the gas supply to the burner on and off in response to a thermally sensitive control located at the boiler. To conserve heat the burner is in :a closely confined combustion chamber which is provided with air by means of a fan only while the burner is lit. Frequently the shut-off valve develops a leak after extended use and gas seeps by the valve into the combustion chamber and causes an explosion when the shut-off valve is again turned on and the burner ignited.

The principal object of the present invention, accordingly, is to provide means for sensing the presence of gas downstream of the shut-off valve when the valve is closed.

Another important object is to prevent the re-ignition of the burner once the flow of gas past the closed shut-off valve is sensed.

Still another object is to provide automatically operating safety means to detect the presence of gas downstream of the shut-off valve when the valve is closed and to automatically prevent the re-ignition of the gas burner subsequent to the detection of gas.

Further objects and advantages will become apparent from the following description taken in conjunction With the accompanying drawing in which:

FIGURE 1 is a semi-diagrammatic showing of one form of the invention applied to a gas fired boiler;

FIGURES 2 and 3 are fragmentary semi-diagrammatic showings of modified forms of the invention; and

FIGURE 4 is an enlarged longitudinal sectional view of a modified form of check valve.

Referring more particularly to FIGURE 1, a gas fired boiler B is shown having a burner to which gas is conducted by the gas line 11. Gas supply line 11 is provided with a solenoid operated shut-off valve 12 and an electrically operated igniter 10' is provided adjacent burner 10 to light the burner when valve 12 is first opened.

A thermostatic or thermo-electric device 13 is provided at boiler B and it will be understood that the heat sensing portion of device 13 operates to open a normally closed switch in the device when the boiler has reached the selected temperature.

Automatic controls represented by a relay 14 are provided for operating valve 12 as demands for heat are signalled by the device 13. A transformer 15, connected to a source of electric current L1, L2, is provided for operation of relay 14 since it is usually advantageous to run such a control circuit at less than line voltage. One control terminal of relay 14 is connected through the switch of device 13 to one pole of the transformer 15 by wires 16 and 17. Wires 18 and 19 normally connect the other control terminal of relay 14 to the other pole of the transformer.

The switch mechanism of relay 14, shown in FIGURE 1 in its normal operating position represented by blades a and b are adapted to open valve 12 by connecting its solenoid to L1 and L2 through the wires 23 and 24, the closed contacts of blades a and b, and wires 21 and 22.

3,225,815 Patented Dec. 28, 1965 The igniter 10' and the fan motor 25 are also shown connected in parallel to wires 23 and 24.

Thus, valve 12 is represented as normally closed and is opened by energizing its solenoid through the energizing of relay 14 when the thermostatic switch 13 is closed by reason of the dropping of temperature in boiler B. With the opening of valve 12, igniter 10' is energized and burner 10 is ignited to heat the boiler. When the desired degree of heat in the boiler is again reached switch 13 opens and blades a and b of the relay return to open position, indicated by broken lines, and solenoid 12 is deenergized and the valve again closes.

Many other arrangements of parts and electrical circuits for obtaining the same results may be devised. Timing and time-delay devices may be employed and a pilot flame may be advantageously used in conjunction with the igniter 10'. Means to disconnect the igniter 10' after the burner 10 is lit are frequently provided, but nine of these devices are shown in the interest of clarity.

The danger, which it is the object of the present invention to eliminate, is that, if valve 12 should leak during periods when the burner is not lit, gas flows through the line 11 to the burner 10 and remains in the combustion chamber because the fan motor 25 is turned off. When igniter 10 is subsequently energized an explosion follows.

To eliminate this danger, a normally closed safety switch 30 is inserted in the control circuit between wires 18 and 19. A pressure sensitive valve 31, shown as an ordinary gravity biased gate check valve, is also provided in the gas supply line between valve 12 and burner 10.

A bleed line 32 is led off from line 11 between valves 12 and 31 and another solenoid operated shut-off valve 33, is provided in the bleed line. The bleed line may, for convenience, be led off from the up stream side of valve 31 as shown.

At the other end of bleed line 32 a jet is provided to form a pilot burner 34 and an electrically operated igniter 34 is provided to light burner 34 if any gas escapes through line 32.

A thermal sensing device is provided in heat association with the pilot burner 34 to open the switch 30 if gas should leak past the valve 12 when it is closed. A thermostatic device is shown at 35 in FIGURE 1 having a diaphragm or other movable part 36 linked to the switch 30 for opening the switch when the heat sensing bulb of the device is heated.

The valve 33 and igniter 34' are connected by wires 37 and 38 to the open contacts of the blades a and b of the relay 14. When the blades a and b are in their open position, a connection is made through wires 21 and 22 to the source of current to open the valve and power the igniter.

The operation of the invention is as follows: During the normal operation of the boiler, burner 10 continues to burn so long as valve 12 is open. So long as valve 12 is open the valve 33 remains closed.

When the thermally operated switch 13 opens because of sufficient heat in the boiler, the control circuit to relay 14 is thereby broken and the relay is deenergized. Blades a and b are released from their normal operating position with closed contacts thereby cutting ofI' current to the valve 12 which reverts to its closed position.

At the same time, blades a and b having returned to their open position shown in broken lines in FIGURE 1, current is supplied to the solenoid of valve 33 to open this valve. Current is also supplied to the igniter 34' so long as blades a and b remain in the open position.

Valve 31 is open when gas under normal line pressure passes through line 11 to the burner 10, but when the valve 12 is closed the valve 31 is biased to close. However, any gas which leaks past valve 12, when it is closed, is at a substantially lower pressure than normal. Valve 31 is gravity biased to remain closed at such lower pressure and leaked gas is therefore by-passed through the bleed line 32 to burner 34. At the burner any gas thus by-passed is ignited by the activated igniter 34'.

The bulb of the thermosensitive device 35, when heated by the flame at burner 34, operates in the usual manner through its capillary tube and moves the diaphragm 36 to open the safety switch 30. Accordingly, when the temperature in the boiler next falls and the sensing device 13 operates to connect wires 16 and 17, the relay 14 is not energized because switch 30 remains open as long as there is a flame at burner 34.

Although the thermal sensing device 35-36 is represented as a vapor pressure operated device it will be apparent that any other known type of thermal sensing device may be used to operate the safety switch 30.

In FIGURE 2 a commercially available switch operating device is represented at 40 connected to bleed line 32' and wires 37 and 38. The box 40 represents a unitary gas sensing device manufactured by Mine Safety Appliance Co. of Mountainside, N. 1., catalogue No. 16,386. The device 40 is provided with an igniter x and burner y which, when ignited, operates a thermoelectric generator 2 to energize relay 41 through the wires 42 and 43 and open switch 30 in the control circuit between wires 18 and 19'.

In FIGURE 3 a pressure operated gas sensing device is represented. Bleed line 32" is connected to a bellows 45 and supported on a frame member 46. The bellows 45 is connected to a lever 47 by a link 48, and the lever carries one contact 30b of a safety switch between wires 18 and 19". Lever 47 is pivotally mounted on member 46 and the other safety switch contact 30a is carried on a fixed arm, not shown, supported by member 46.

When gas leaks past the valve 12, it is by-passed through the bleed line 32 by the pressure-sensitive valve 31. Bellows 45 is adapted to expand at a pressure less than the bias with which valve 31 is closed, so that the bellows expands and breaks the electrical connection between contacts 30a and 30b when any appreciable amount of gas leaks past the valve 12.

In FIGURE 4, a pressure sensitive valve 50 is shown in which the bias closing the valve at less than normal gas-line pressure is adjustable.

The direction of flow of gas through supply line 11 is indicated by the arrow G through the body 51 of valve 50. A port 52 in the valve seat is closed by a valve 53 which is carried on a gate arm 54 hingedly secured at 55 within the body 51. Gate arm 54 is provided with two upwardly projecting lugs 56 between which a spring carrier 57 is hingedly secured by a pivot pin 58. The usual cap 59 of valve 50 is provided with an adjustment screw 60 threaded therethrough. The lower end of screw 60 is provided with a spherical projection or ball 61 and a spring retaining cap 62 is clinched about the ball so as to swivel thereon.

One end of an extension coil spring 63 is engaged by the rod-like end of carrier 57 and the other end of the spring engages ball 61 within cap 62. A nut 64 and sealing washer 65 are provided for sealing the adjustment screw in cap 59. The usual pipe plug 66 is provided as a bumper for the turned-up end of gate arm 54.

Nut 64 may be loosened and screw 60 advanced within the cap 59 to increase the compressive tension on spring .63 for increasing the closing bias on valve 53 or screw 64 may be backed off to decrease the bias.

While the normal gas pressure in the supply line 11 is not great, it will be apparent that spring 63 may be dimensioned and screw 60 adjusted to operate at any selected pressure less than normal gas pressure without impeding the flow of :gas to burner when valve 12 is open, and to keep valve 53 closed so as to by-pass all gas leaking by valve 12 when the latter is closed. This valve is especially useful in the modified form of the invention shown in FIGURE 3.

While the location of the safety switch in the control circuit for relay 14 is preferred in order to make the safety device automatic, it will be understood that the gas sensing devices shown in FIGURES 1-3 can also be used to operate a warning signal, to turn on the fan motor 25, or to operate other devices for preventing subsequent reignition of the burner 10.

As will be apparent to those familiar with the art, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed are therefore to be considered in all respects as illustrative rather than restrictive, the scope of the invention being indicated by the appended claims.

What is claimed is:

1. A safety device for signalling a leak past an automatically operated supply valve in a line for supplying ga at a normal pressure, comprising: a pressure sensitive valve in the supply line downstream from the supply valve, said pressure sensitive valve having a gate that opens under normal gas pressure in the line and is biased toward closed position at less than normal gas pressure, a bleed line connected in the supply line between said supply valve and said biased gate, automatically operated valve means in said bleed line, means for closing said last-named valve when the supply valve is open and opening said last-named valve when the supply valve is closed, and means at the end of the bleed line for sensing the presence of gas escaping therefrom whereby a leak in the supply valve can be detected.

2. A safety device for a heating system using combustible gas under a substantially constant normal pressure, which system includes an automatically operated supply valve for intermittently shutting off and turning on the flow of gas in a gas supply line according to the demands of the system, and including means for igniting the gas when the supply valve is turned on, comprising: a pressure sensitive valve in the supply line downstream from the supply valve, said pressure sensitive valve having a gate that opens under normal pressure in the line and is biased toward closed position at less than normal pressure in the line, a bleed line connected in the supply line between said supply valve and said biased gate, automatically operated valve means in said bleed line, said last named valve means being closed when the supply valve is open and open when the supply valve is closed, and means at the end of the bleed line for sensing the escape of gas from the end of the bleed line, said sensing means being operably connected in the system for automatically preventing the operation of the ignition means following a period in which the supply valve is turned off and the presence of gas is detected by said sensing means.

3. A safety device for employment in a system using combustible gas under pressure, which system includes an automatically operated valve for intermittently shutting off and turning on the flow of gas in a gas supply line to a combustion chamber and re-igniting the resumed flow of gas according to the demands of the system, comprising: a pressure operated valve in the gas supply line between said automatically operated valve and said combustion chamber; said pressure operated valve having a gate that opens at normal pressure in the line and is biased to a closed position when there is less than normal pressure in the line; a bleed line connected at one end to said supply line between the automatically operated valve and the pressure operated valve; an automatically operated valve in said bleed line adapted to close when the shut off valve in the supply line is open and to open when the shut off valve is closed; means at the other end of said bleed line for detecting the flow of gas through said bleed line; and means operable by said gas detecting means for preventing the subsequent re-ignition of said gas in the combustion chamber.

V 4. A safety device for employment in a system using gas under a normal pressure, which system includes a gas supply line and a first valve therein electrically operable to open and close by an operating circuit, the Operating circuit including means to ignite the gas when the valve is opened comprising: a check valve in said line downstream from said first valve biased to prevent the flow of gas under a pressure less than normal and pressure operable to open under normal pressure of the gas; a bleed line connected at one end to said supply line between said first valve and said check valve; a second electrically operated valve in said bleed line adapted to open when said first valve is closed and to close when said first valve is open; means for detecting the flow of gas at the other end of said bleed line; a switch in the operating circuit to said first valve and said ignition means; and switch operating means operable by said gas detecting means for opening said switch when a flow of gas is detected through said bleed line.

5. In an automatically operated gas-fired boiler having a gas burner, a gas supply line, an electrically operated shut-off valve in the line, electrically operated switching means for alternately opening the valve and igniting the burner and then shutting off the valve, and therrnosensitive means for controlling the switching means, a safety device comprising: a second valve in the supply line between said first mentioned shut-off valve and the burner, said second valve being biased to prevent the flow of gas under pressure less than normal and to open to permit the flow of gas at normal pressure, a bleed line connected at one end to the supply line between the first mentioned and second valves; a third shut-off valve in said bleed line electrically operable through the switching means to open when the first mentioned valve i closed and to close when the first valve is open; gas detecting means at the other end of said bleed line; a normally closed switch in the circuit connecting the thermosensitive control means and the switching means; and means initiated by said gas detecting means for opening said norm-ally closed witch when gas flows through said bleed line to prevent re-ignition of the burner when there is a leak past the first mentioned valve.

6. A safety device for preventing explosions in an automatically operated gas-fired boiler having a combus tion chamber, a gas burner in said chamber, a gas supply line to the burner, a first valve electrically operated to shut oif the flow of gas in said line, electrically controlled means for igniting said burner, first switch means operable by thermal sensing means in said boiler, and a second electrically operated switch means controlled by said first switch means for completing a circuit to said first valve to move said first valve from closed to open and for operating said igniting means, a second valve in said line between the first valve and the burner, said second valve being adapted to open when the first valve is open and gas under normal pressure reaches said second valve and being spring-biased to prevent the flow of gas therethrough when the first valve is closed and gas under less than normal pressure leaks by said first valve; a bleed line connected at one end to said supply line between said first and second valves; a third valve in said bleed line electrically operable to shut off the flow of gas therethrough; third switch mean electrically operated simultaneously with said second switch means for closing said third valve when said first valve is open and for opening said third valve when said first valve is closed; gas detecting means at the other end of said bleed line; a norm-ally closed safety switch in the circuit controlled by said first switch means; and means for opening said safety switch when a flow of gas through said bleed line is detected to prevent operation of said burner igniting means.

7. The safety device as defined in claim 6 wherein said gas detecting means and safety switch opening device comprise: a pilot burner at the end of the bleed line, an electrically operated igniting device for lighting said pilot burner, and a thermostatic sensing device in heat association with said pilot burner and mechanically connected to open said safety switch, said pilot igniting device being electrically connected in circuit with said third valve and third switch means for igniting said pilot when the third valve is open.

8. The safety device as defined in claim 6 wherein said gas detecting means and safety switch opening 'device comprise: a pilot burner at the end of the bleed line, an electrically operated igniting device for lighting said pilot burner, a thermoelectric sensing device in heat association with said pilot burner, and electromagnetic means for operating said safety switch, said electromagnetic means being electrically connected to said thermoelectric sensing device, said pilot igniting device being electrically connected in circuit with said third valve and third switch means for igniting said pilot when the third valve is open.

9. The safety device as defined in claim 6 wherein said gas detecting means and safety switch opening device comprise: pressure expandable means connected to the end of said bleed line, said expandable means operably connected to open said safety switch when the expandable means are expanded by gas under pressure in the bleed line.

10. A gas burner system control, comprising: a gas supply line to the main burner, a first solenoid operated shut-off valve in the line, an electrically operated igniter associated with the burner, a thermally operated control switch for regulating the burner according to the heat demand of the system, a relay in circuit with said control switch, a normally closed safety switch in said relay circuit, a gate valve in the gas supply line between the first valve and the burner, said gate valve being biased to open under full pressure in the line and to close at a pressure less than full pressure, a bleed line connected at one end to the gas supply line between the first shut-off and gate valves and adapted at its other end as a safety burner, a second electrically operated igniter associated with said safety burner, a second solenoid operated shutoff valve in the bleed line, and a thermally controlled operating device in heat association with said safety burner for opening said safety switch, said relay having switch means adapted to move in response to movements of said control switch to alternate positions in which said shut- 01f valves and igniters are connected with a source of electric power so that when the line associated with one shut-off valve is open the other line is closed and vice versa and the igniter associated with the burner at the end of the open line is activated, whereby, when said first shut-off valve fails to completely close, said safety switch in the control circuit is opened to prevent subsequent starting of the main burner.

11. A gas burner system control comprising: a gas supply line to the main burner, a first solenoid operated shut-off valve in the line, an electrically operated igniter associated with the burner, a thermally operated control switch for regulating the burner according to the heat demand of the system, a relay in circuit with said control switch, a normally closed safety switch in said relay circuit, a gate valve in the gas supply line between the first valve and the burner biased to open under full pressure in the line and to close at a pressure less than full pressure, a bleed line connected at one end to the gas supply line between the first shut-oif and gate valves and connected at its other end to a pressure responsive device, said pressure responsive device being operatively connected to said safety switch to open the switch when the device responds to pressure, and a second solenoid operated shut-off valve in the bleed line, said relay having switch means adapted to move in response to movements of said control switch to alternate positions in which said shut-off valves and the igniter are connected with a source of electric power so that when the line associated with 7 7 8 one shut-oif valve is open the other line is closed and vice 2,585,882 2/ 1952 Weissman et al. 15 8122 versa and when the first shut-off valve is open the igniter 2,730,169 1/1956 Deubel 158125 X is activated, whereby, when said first shut-off valve fails 2,913,044 11/1959 lvfobley 158122 to completely close, said safety switch in the control cir- 2,944,596 7/1960 Sager 158-125 X cuit is opened to prevent subsequent starting of the main 5 3,086,583 4/ 1963 Reichow 158-125 burner.

References Cited by the Examiner OTHER REFERENCES UNITED STATES PATENTS German printed application, 1,128,823, May 1962.

1,330,265 2/1920 Hinton 137-527 I 2,482,198 9/1949 Melichar 10 FREDERICK L. MATTESON, JR., Plzmaly Examzne).

2,532,214 11 /195() win JAMES W. WESTHAVER. Examiner. 

1. A SAFETY DEVICE FOR SIGNALLING A LEAK PAST AN AUTOMATICALLY OPERATED SUPPLY VALVE IN A LINE FOR SUPPLYING GAS AT A NORMAL PRESSURE, COMPRISING: A PRESSURE SENSITIVE VALVE IN THE SUPPLY LINE DOWNSTREAM FROM THE SUPPLY VALVE, SAID PRESSURE SENSITIVE VALVE HAVING A GATE THAT OPENS UNDER NORMAL GAS PRESSURE IN THE LINE AND IS BIASED TOWARD CLOSED POSITION AT LESS THAN NORMAL GAS PRESSURE, A BLEED LINE CONNECTED IN THE SUPPLY LINE BETWEEN SAID SUPPLY VALVE AND SAID BIASED GATE, AUTOMATICALLY OPERATED VALVE MEANS IN SAID BLEED LINE, MEANS FOR CLOSING SAID LAST-NAMED VALVE WHEN THE SUPPLY VALVE IS OPEN AND OPENING AND LAST-NAMED VALVE WHEN THE SUPPLY VALVE IS CLOSED, AND MEANS AT THE END OF THE BLEED-LINE FOR SENSING THE PRESENCE OF GAS ESCAPING THEREFROM WHEREBY A LEAK IN THE SUPPLY VALVE CAN BE DETECTED. 